In networking of mobile communication systems, a local area network is partitioned and set generally according to geographical locations and the number of terminals. In areas of sparse population, it is suitable to have a large local area network that covers several small subnets in order to achieve a closer access and a wide coverage. The large local area network refers to a network covered by one physical MSC, and it is partitioned into subnets based on geographical locations to obtain small local area networks.
The large local area network includes a Base Station (BS), a Base Station Controller (BSC), an MSC, a Visited Location Register (VLR) and a Home Location Register (HLR). The BS (BTS/Node B) receives and transmits wireless signals, and serves a certain area, and communicates with terminals in the area. The BTS/Node B is connected with a Base Station Controller/Radio Network Controller (BSC/RNC), which manages radio resources and controls the base station. The BSC is connected to the MSC through a Media Gateway (MGW) or directly. The MSC is mainly used for controlling the mobile calling procedure. The VLR is a database to store temporary information of terminals; and the information is needed when the MSC visits the terminal. The HLR is a database to permanently store management information of the terminals and service records of the terminals.
FIG. 1 shows a network structure which includes three subnets and is covered by one physical MSC. In FIG. 1, the MSC/VLR covers location area 1, location area 2 and location area 3; the location area 1 further includes two location zones: LAI 11 and LAI 12, the location area 2 includes one location zone: LAI 2, and the location area 3 includes one location zone LAI 3. It can be seen that the whole network includes one physical and logical MSC/VLR and one HLR that controls all the terminals in the network and generates billings and traffic statistic. The existing method of distance measurement between a calling party and a called party is implemented with the MSC/VLR number. Since there is one logical MSC/VLR, the whole large local area network uses the same MSC number. The billing and traffic statistics of terminals communicating in different small local area networks, are the same as those of terminals communicating in a small local area network.